Coating dissolution rate

The approximate value for the oxide coating dissolution rate in relation to current density in soils and fresh water is ... 

Release of an ingredient from a particle coated with a soluble coating will be influenced by the coating dissolution rate. 

Coated fertilizers achieve controlled release by coating a soluble fertilizer core (substrate) with a water-insoluble barrier which limits the access of water to the fertilizer and thus limits its dissolution rate. 

Yagi and Wakao (1959) used mass transfer measurement results to estimate the heat transfer coefficient at the tube wall. Material was coated on the inner surface of the packed tubes and the dissolution rate was measured. 

In plain tinplate cans for acid foods, tin provides cathodic protection to steel (3,4). The slow dissolution of tin prevents steel corrosion. Many investigators (5-1I) have defined this mechanism in detail and have shown that the tin dissolution rate is a function of the cathodic activity of the base steel, the steel area exposed through the tin and the tin-iron alloy layers, and the stannous ion concentration. Kamm et al. showed that control of the growth of the tin—iron alloy layer provides a nearly continuous tin-iron alloy layer and improves the corrosion resistance of heavily coated (over 45 X 10"6 in. tin) ETP for mildly acid food products in which tin provides cathodic protection to steel (12). The controlled tin-iron alloy layer reduces the area of steel exposed to the product. ETP with the controlled alloy is designated type K, and since 1964, 75 type K ETP has been used to provide the same protection as 100 ETP provided previously (13). 

MCFC Cathode Protective coatings to decrease dissolution rate... 

Acid Concentration Required for Crosslinking Resist Films. The strong acid catalyzed reaction of methylated melamine 1 with novolak in a film was studied first in order to estimate the amount of acid generated in experimental AHR resists upon exposure. Incremental amounts of a 1% solution of p-toluenesulfonic acid (pTSA) were added to a resist solution which contained no RSAG. The solutions were coated onto wafers and subjected to a typical bake cycle. The dissolution rate... 

The flow-through cell is applicable not only for the determination of the dissolution rate of tablets and sugar-coated tablets, but has also been applied to suppositories, soft-gelatin capsules, semisolids, powders, granules, and implants. A small volume cell containing the sample solution is subjected to a continuous stream of dissolution media. The dissolution... 

A recent addition to General Chapter Dissolution <711> allows for the addition of enzyme to the dissolution medium. This is justified when gelatin-coated tablets or gelatin-encapsulated products exhibit a slow-down in the dissolution rate attributed to the crosslinking of the gelatin. The addition of enzyme will break up the crosslinking and therefore remove the... 

In summary, the lag time of drug release may be controlled by the rate at which water penetrates through the coating or shell, the rate of fluid absorption of the polymer layer, the osmotic activity of salts and osmopolymers, the erosion and dissolution rate of the polymer layers and the thickness of the layers or coatings. 

Triazones form ammonium ions much more slowly than urea. Slow-release potassium is also being developed. A coating of sulfur seems to delay its release. For phosphorus Mg(NH4)P04 is becoming popular because it has a slower dissolution rate in the soil. Despite the simple chemicals used in most fertilizers, some interesting research and formulation work will keep chemists involved in the industry for some time to come. 

Faraday s Law applies to the anode as well as to the cathode ie, the total reaction at the anode is proportional to the current, and much like the cathode, the anode efficiency varies with the current density. As the current on the anode is increased, the anode efficiency decreases, slightly at first, until it reaches a point at which the anode metal cannot dissolve fast enough through the anode film. The first stage of dissolution for the soluble anode is the oxidation of the metal followed by dissolution of the oxide. When the oxide dissolution rate is less than the oxidation rate, polarization of the anode takes place. The oxide film builds up in sufficient thickness to form an insulating coating, and the current decreases rapidly. The thick anode films can dislodge at... 

A mathematical analysis was presented and applied to release of drug from benzphetamine pamoate pellets. When the acid coat forms, the dissolution rate can be reduced essentially to that ofthe poorly soluble acid (Higuchi et al., 1965). 

While particle size continues to be the physical property most frequently determined by NIR spectroscopy, several other parameters including the dissolution rate and the thickness and hardness of the ethylcellulose coating on theophylline tablets have also been determined using NIR, all with good errors of prediction.94 Tablet hardness, which dictates mechanical stability and dissolution rate, has been determined in hydrochlorothiazide tablets.95... 

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